PP-Vac is a freeze dried live pigeon pox virus vaccine, propagated in chicken embryos, used for wing web vaccination of chickens 8 weeks of age or older against fowl pox. It gives flock owners a practical, well established option for pox control.Key Uses Active immunization of healthy chickens against fowl pox virus Labeled for chickens 8 weeks of age or older Given by wing web stab using a double needle applicator Successful takes appear as swelling or a scab at the injection site around 5 to 7 days post vaccination, with immunity developing by about 21 days Administration and Safety NotesDo not vaccinate within 4 weeks of the start of lay, and vaccinate all susceptible birds on the premises at the same time. Merck's label lists a 21 day pre-slaughter interval; confirm current withdrawal guidance with your veterinarian.